Arrector pili

Arrector Pili is a tiny muscle found in the human body, attached to hair follicles in the skin. The contraction of these muscles causes the hairs to stand on end, a phenomenon known as 'goosebumps' or 'piloerection'.

Anatomy

The arrector pili muscle is a small band of smooth muscle tissue extending from the dermal sheath of the hair follicle to the papillary layer of the dermis. It is innervated by the sympathetic branch of the autonomic nervous system.

Function

The primary function of the arrector pili is to regulate hair position and manage heat retention. When the body is cold, the arrector pili muscles contract, causing the hair to stand on end and trap a layer of air to insulate the skin. This is also the cause of the 'goosebumps' phenomenon, which can also occur in response to fear or other strong emotions.

Clinical significance

Abnormal function of the arrector pili muscles can lead to conditions such as alopecia, a type of hair loss, and hyperhidrosis, excessive sweating. In addition, they can be affected in certain skin diseases such as acne and rosacea.

See also

• Hair follicle
• Goosebumps
• Piloerection
• Autonomic nervous system